Using a webservice with blocks and returning data via callback

Question

I load some data from from my webservice via a method using blocks and callbacks.

From my ViewController I make a request to the data loading class and pass the callback block:

- (void)loadRadioStationList
{
 [self.radioDataLoader getRadioStationList:^(NSArray *data, NSDictionary *dictData){
 self.alphabetizedDictionary = [[NSDictionary alloc] initWithDictionary:dictData];
 self.sectionIndexTitles = [[NSArray alloc] initWithArray:data];
 [self.radioStationTableView reloadData];
 }];
}

Then in the dataloading class the method is as so:

-(void) getRadioStationList:(void (^)(NSArray *data, NSDictionary *dictData))callback
{
 NSString *string = RadioStationListURL;
 NSURL *url = [NSURL URLWithString:string];
 NSURLRequest *request = [NSURLRequest requestWithURL:url];
 AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];
 operation.responseSerializer = [AFXMLParserResponseSerializer serializer];
 [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject) {
 NSXMLParser *XMLParser = (NSXMLParser *)responseObject;
 [XMLParser setShouldProcessNamespaces:YES];
 XMLParser.delegate = self;
 [XMLParser parse];
 callback((NSArray*)self.sectionIndexTitles, (NSDictionary*)self.alphabetizedDictionary);
 } failure:^(AFHTTPRequestOperation *operation, NSError *error) {
 UIAlertView *alertView = [[UIAlertView alloc] initWithTitle:@"Error Retrieving Radio List"
 message:[error localizedDescription]
 delegate:nil
 cancelButtonTitle:@"Ok"
 otherButtonTitles:nil];
 [alertView show];
 }];
 [operation start];
}

It loads the XML file and parses out the data and send the data back to my VC via the callback block.

I've a couple of questions:

1. Is this an acceptable way of doing this? Would you prefer to see it done another (better) way?
2. If I was to write an API, would passing the data from the API back to the calling class be a good way to work it, or is there a more suitable method for an API?

Answer 1

Here is a way how I do it:

Create a class and name it like ClientApi. This class should be a singleton link and be absolutely independent. Also, create a class APIRouter which will return a path for a request. I'm using the AFNetworking framework for communication with different API etc. and JSONModel framework for mapping. Here you can find the full answer about network architecture in iOS apps.

@interface SFAPIClient ()
@property (nonatomic, strong) AFHTTPSessionManager *manager;
@end
@implementation SFAPIClient
+ (instancetype)sharedInstance
{
 static id _sharedInstance = nil;
 static dispatch_once_t onceToken;
 dispatch_once(&onceToken, ^{
 _sharedInstance = [[[self class] alloc] init];
 });
 return _sharedInstance;
}

If a request should return some data, pass block as a parameter to the method:

- (void)getAllChildsWithCompletion:(void(^)(NSArray *arr, NSError *error))completion
{
 NSString *url = [SFAPIRouter childRoute];
 [self setupRequestSerializer];
 [self.manager GET:url parameters:nil progress:nil success:^(NSURLSessionDataTask * _Nonnull task, id _Nullable responseObject) {
 NSError *error = nil;
 NSArray *arr = //map respons
 if (!error)//if everything good call block with data 
 completion(arr, nil);
 else
 completion(nil, error);
 } failure:^(NSURLSessionDataTask * _Nullable task, NSError * _Nonnull error)
 {
 if (completion)
 completion(nil, error);
 }];
}

APIRouter:

static NSString * const kSFServerURL = @"http://0.0.0.0/api/v1";
@implementation SFAPIRouter
+ (NSString *)saveMediaToListRoute
{
 return [kSFServerURL stringByAppendingString:@"/childs"];
}

And then in controller call function from your ClientApi class:

//show activity indicator
[[SFAPIClient sharedInstance] getAllChildsWithCompletion:^(NSArray *arr, NSError *error){
//stop showing activity indicator
if (error)
{
//show alert
return;
}
//do what you need
}];